A French submarine begins the search Wednesday for the flight recorders that may contain clues as to why Air France Flight 447 crashed into the Atlantic Ocean last week.
A French military spokesman, Christophe Prazuck, says the nuclear-powered submarine will begin patrolling an initial search zone of 36 kilometer by 36, with search areas changed daily.
If the recorders are found, unmanned robot submarines on board a French vessel, the Pourquois Pas, could be used to bring them in.
The recorders, known as "black boxes," have voice recordings and data from the final minutes of Flight 447. They are believed to be on the ocean floor at depths of at least 3,000 meters. The recorders emit signals for 30 days after crashes.
The Airbus A330 was carrying 228 passengers and crew when it crashed while on route to Paris from Rio de Janeiro. Crews have so far pulled 41 bodies from waters off the Brazilian coast.
Investigators have been focusing on the possibility that a problem with the jet's speed sensors, known as Pitot tubes, may have led to the deadly crash.
A pilots' union said Tuesday that Air France is replacing the sensors on its Airbus jets with newer versions and has promised not to allow any A330 or A340 models to fly unless at least two of their three monitors are changed.
Theories being investigated include the possibility that the sensors iced over during a thunderstorm and gave false readings to the cockpit. Aviation experts say the false data could have caused the pilots to fly too slowly and stall, or too fast and lead the air frame to rip apart.
Search teams have recovered a large tail section that was sheared off the plane.
Some information for this report was provided by AFP and Reuters.